Field of Invention
The present disclosure relates to a motor.
Discussion of the Related Art
This section provides background information related to the present disclosure which is not necessarily prior art.
In general, a rotor of brushless motor is configured by press-fitting a shaft into a center of a rotor core and installing a permanent magnet on a periphery. At this time, the permanent magnet may be attached while being exposed to an outside of the rotor core, and a permanent magnet accommodation groove unit may be formed at a position near to the periphery of the rotor core, and the permanent magnet may be inserted into the accommodation groove unit.
In a case the permanent magnet is installed while being exposed to the periphery of the rotor core, there may be an advantage of minimizing the magnetic flux loss, but there is also a disadvantage of the permanent magnet being separated during rotation of the rotor core due to centrifugal force of the rotor core rotating at a high speed, in a case the motor is used for a long time or under a harsh condition. In order to solve the aforementioned disadvantages, a can member formed with resin material for preventing particles in the permanent magnet from scattering is covered on a surface of the permanent magnet, which however disadvantageously deteriorates motor torque due to increased air gap at the magnetic field.
Meanwhile, in a case a permanent magnet accommodation groove unit is formed inside the rotor core, and the permanent magnet is inserted into the permanent magnet accommodation groove unit, the permanent magnet is prevented from being separated, but the motor suffers from another disadvantage in that a motor efficiency relatively deteriorates due to loss in magnetic field because the permanent magnet is positioned inside the rotor core.
In order to prevent the magnetic field from being lost, there is a need of using a permanent magnet having a magnetic force relatively greater than that of a permanent magnet attached to the surface of the rotor core. Generally, a neodymium rare earth magnet is largely used for a permanent magnet having a stronger magnetic force. The neodymium rare earth magnet is a strong permanent magnet formed with rare earth element Nd—Fe—B, and called a neodymium super magnet.
Meanwhile, the neodymium rare earth, one of the main raw materials forming the neodymium rare earth permanent magnet is largely produced in China, and a manufacturing cost of the rotor core has greatly increased recently due to sudden price rise in the rare earth materials. Thus, development of rotor is required recently using a permanent magnet of ferrite material free from rare earth elements, as the increased manufacturing cost of rotor core acts to increase the motor cost.
However, in a case the permanent magnet of ferrite material is used for a rotor of IPM method where the permanent magnet is inserted into a rotor core, saturation of magnetic field is not realized at a rib portion formed in a plurality of cores for inserting a magnet of the rotor core due to relatively weaker magnetic force than that of the conventional rare earth magnet, such that torque becomes relatively weaker due to weak flux linkage and the like, which therefore needs improvement.
Meanwhile, a conventional BLDC (Brushless Direct Current) motor includes a stator installed on a motor housing or a frame, a magnet rotor rotatably inserted into the stator, and a shaft fixedly inserted into a center of the magnet rotor. The stator is formed by a stator core wound by a coil. The stator core is manufactured by stacking a plurality of silicon steel plates, each with a thickness of less than 1 mm, which are punched by a press, where each silicon steel plate includes a cylindrical yoke unit, a plurality of teeth units protruded toward a center of an inner surface of the yoke unit along a circumferential direction, each spaced apart at a predetermined distance, and polarized pole units protrusively formed at distal ends of the teeth unit.
A plurality of slots to be wound by the coil is formed among the teeth units, where the slots are inserted by an insulator of insulating material for insulation between the stator core and the coil. The insulators are air-tightly inserted from both sides into the slots along a stacking direction of the stator core. Meanwhile, the coil may be wound to correspond to polarity of used power, and in a case a 3-phase (U, V, W) power is used, the coils are conductibly connected to mutually different terminals of three polarities. Furthermore, the insulator is integrally provided with a terminal housing coupling unit, where a terminal housing for power supply is press-fitted into the terminal housing coupling unit.
However, in the terminal housing coupling unit formed at the insulator, there may be generated short-circuit in the coils applied with mutually different polarities at a position where the coil and the terminal are conductibly connected. That is, the coils respectively wound on the insulator are alternatively crossed at a connection unit for being wired to a terminal of each polarity, where, although each coil is protected by coating, and if the coating is damaged by repetitive shock and friction, each coil may be short-circuited. In a case each coil of mutually different polarity is generated with short-circuits, the motor may disadvantageously develop a defect including rotation stop and the like.